The present invention relates to a printing device, particularly for use with a portable label printing and applying machine (which is referred to as a "hand labeler"), and more particularly relates to improvements in an index wheel for the printing device.
Generally, these printing devices are either the type wheel type (see U.S. Pat. Nos. 4,055,118, 4,018,157 and 4,084,507) or the type band type (see U.S. Pat. Nos. 4,055,118 and 4,179,989). In the former type wheel type, a plurality of type wheels are coaxially juxtaposed to one another. Each index wheel is engageable with a corresponding type wheel to rotatively drive the type wheel when the index wheel is manually rotated through a selecting shaft by means of a selecting knob. The index wheels bear index letters or characters. The index wheels are usually molded of a plastic, and are molded as a whole unit, including the letters or characters. Numerous kinds of molds have to be prepared for index wheels which have different arrangements and combinations of the index letters. This raises production costs to a remarkably high level.
In view of this problem, there is another construction, in which the index letters are not molded but are instead printed on the outer circumference of an inner index wheel member and are covered with an outer index wheel member which is toothed on its outer circumference and is made of transparent plastic. Since the index letters have to be read out through the transparent outer index wheel member, they may be apparently distorted or doubled so that they frequently become hard to read. Moreover, when the outer index wheel member is to be fused to the outer circumference of the inner index wheel member, the printed index letters are thermally deformed or bubbles become confined in the outer index wheel member so that the index letters also are hard to read.